chore: remove duplicate credentials/ dir + add CLAUDE.md + .claude rules

credentials/ was a leftover duplicate — all credential routes already live
in cypher-executor/src/routes/credentials.ts. Adds the SDD protocol,
tech-stack, forbidden-list, component-architecture, and progress rules
that guide Phase 1-6 refactors.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.claude/settings.json

@@ -0,0 +1,61 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "matcher": "startup|resume|clear",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash .claude/hooks/session-start-load-sdd.sh",
+            "timeout": 5
+          }
+        ]
+      }
+    ],
+    "PreToolUse": [
+      {
+        "matcher": "Write|Edit|MultiEdit",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash .claude/hooks/pre-write-guard.sh",
+            "timeout": 5
+          }
+        ]
+      },
+      {
+        "matcher": "Bash",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash .claude/hooks/pre-bash-guard.sh",
+            "timeout": 5
+          }
+        ]
+      }
+    ],
+    "PostToolUse": [
+      {
+        "matcher": "Write|Edit|MultiEdit",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash .claude/hooks/post-edit-remind-tasks.sh",
+            "timeout": 5
+          }
+        ]
+      }
+    ],
+    "Stop": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash .claude/hooks/stop-check-sync.sh",
+            "timeout": 5
+          }
+        ]
+      }
+    ]
+  }
+}